1. Field of the Invention
The invention relates to a filter unit for liquids that can freeze, in particular, for a metering unit of an exhaust gas treatment unit, comprising at least one filter insert arranged in a housing that comprises an outer member and a lid member.
2. Description of the Related Art
In known filter units of this kind, an aqueous solution or liquid, for example, an urea solution, a saline solution, water or the like, is guided through a filter unit by means of a pump and is then supplied at a certain pressure to a metering unit, for example, of an exhaust gas treatment device. When the aqueous medium freezes, a medium-specific volume expansion occurs. This volume expansion is between approximately 6% up to approximately 10%. Since in the known filter units the outer housing member is comprised of metal, the volume expansion causes permanent damage of the housing already after a relatively short period of time.